Check out this site...
http://www.bigpawsonly.com/biggest-dog-features.htm
The Biggest, Largest Dog - the Mastiff
The biggest dog (and breed of dog) in terms of mass is the English Mastiff, with Zorba the OEM taking the crown. From the U.K., Zorba weighed in at
343 lbs and measured almost 8 feet long from nose to tail. English Mastiffs are considered the biggest dogs as they are usually the heaviest dogs with weights over 200 lbs. not uncommon.
Giant Dog Reference:
Irish Wolfhound: weight: 105-125 lbs. height: 35-35 in.
Great Danes: weight: 100-120 lbs. height: 28-32 in.
English Mastiff: weight: 175-190 lbs. height: 27.5-30 in.
Neopolitan Mastiff: weight: 150-180 lbs. height: 26-31 in.
Newfoundland: weight: 130-150 lbs. height 28-30 in.
Saint Bernard: weight: 150-200 lbs. height: 27-30 in.
* Height is measured at the shoulder *
Might not be a chop. Did you check out Guiness Book Of World Records?